reverse engineering help

Discussion in 'General Electronics Chat' started by atntias, Oct 21, 2013.

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  1. atntias

    Thread Starter New Member

    Oct 21, 2013
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    Hi,
    I have a circuit meant to control AC solenoids, and using TRIACS to do so, and I'm trying to externally control it.
    Its seemed fairly simple so I started measure voltage and make sens of the board, and as soon as i connected a scope the whole thing blew up :p, So...I got a replacement board and made a full schematics of it.

    It uses an atmega8, I might be able to reprogram it to my purpose or replace it with an arduino chip, either way the impotent part is to understand how the triacs control the coils, and how not to blow the board agian.

    the board takes a 220V input, and controls 4 coils, the board allows intensity and rhythm control, my guess so far is that an pulse at the base of the 2222a somehow determines the amplitude of the ac voltage and 0 is off... not sure..
    but before i try to poke the board again id appreciate any advice, and some DO's And DONT's for the board.

    here is a LINK to the eagle schematic all the values and part numbers are accurate. U3 is just a low voltage detector, TH1 looks lke a cap but behaves like a short, not sure what it is.., R999 is a fix to the board that looks like it was done manually after manfuactering, feel free to ak any question, verfy anything, request tests or mesures...

    attached some pics
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    thanks! atntias
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,547
    2,373
    The reason apparently that is blew is your scope probe is at earth ground potential usually, and the Triac 240 supply appears to be common to your logic board common, IOW there is no isolation on the incoming 240vac.
    It either requires a Mains isolation transformer or use opto isolators on the input to the triacs.
    There are Triac opto isolators that are made specifically for firing the triac with isolation.
    This way you can keep the two power supplies separate.
    Max.
     
  3. #12

    Expert

    Nov 30, 2010
    16,295
    6,807
    Besides the fact that you think upside down, there is no transformer for the 5V supply, I can't tell which country you are in so I don't know whether the 220VAC is single phase or split phase, this method is not allowed on this site.
     
  4. atntias

    Thread Starter New Member

    Oct 21, 2013
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    0
    hi, thanks for your replay, i understand that this crcuit used some wierd dc regulation and does not seperate the ac, but it is a product that works and works well, and wasnt designed by me, im just trying to understand, two things.

    1. assuming im able to control the proseccor, what output should i generate to control the coils
    2. how can safly monitor the output of the microcontroller if the ground of the scope is giving problems, if i can see what the out put looks like i will be able to understand it..
     
  5. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    Your thread revolves around a restricted topic, as can be read in the Terms of Service of the forum, Chapter 6:
    http://www.allaboutcircuits.com/l_tos.html

    The AAC administration has chosen not to allow discussions on transformer-less power supplies, hence this thread will be closed.
     
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